Beam sweep or scan in a wireless communication system

ABSTRACT

A user equipment is configured for use in a wireless communication system. The user equipment in this regard is configured to detect an orientation of an equipment coordinate frame defined for the user equipment relative to an earth coordinate frame defined for Earth. The user equipment is also configured to determine, based on the detected orientation, a set) of beams defined in the equipment coordinate frame which does not include any beam pointing in one or more predefined directions in the earth coordinate frame. The user equipment is further configured to perform a beam sweep or scan on the determined set of beams.

TECHNICAL FIELD

The present application relates generally to methods and apparatus in awireless communication system, and particularly methods and apparatusrelated to a beam sweep or scan in a wireless communication system.

BACKGROUND

A transmitter employs beamforming in order to amplify transmittedsignals in selected directions, while weakening them in others. Tobeamform, the transmitter transmits a signal from multiple transmitantennas, but with individually adjusted phase shifts or time delays.This effectively creates a transmit beam in a desired transmit radiationdirection of the signal—e.g., through controlled constructive anddestructive interference of the phase-shifted signals from individualantenna elements. A transmitter performs a so-called beam sweep in orderto determine which of multiple possible transmit beams to use fortransmitting to a receiver. The transmitter in this regard transmitsknown signals on different candidate transmit beams and selects for datatransmission whichever of those transmit beams the receiver indicates asbeing received the best. A typical beam sweep could consist of a set ofadjacent beams transmitted one after the other until the entire intendedcoverage area, e.g. a cell, has been covered.

Correspondingly, a receiver employs beamforming in order to amplifysignals received from selected directions while weakening unwantedsignals in other directions. The receiver does so by using phase shiftsbetween antenna elements to steer the maximal antenna sensitivity towarda desired direction. This effectively creates a receive beam in thedesired direction. A receiver performs a so-called beam scan in order todetermine which of multiple possible receive beams to use for receivingfrom a transmitter. The receiver in this regard receives on differentcandidate receive beams and selects whichever of those receive beamsyields the best receive performance.

A beam sweep or scan improves transmit or receive performance. However,a beam sweep or scan threatens to increase transmit/receive delay, radioresource consumption, energy consumption, and interference due totransmission or reception on multiple beams. This in turn reduces theperformance of handover, initial access, or other procedures for whichthe beam sweep or scan may be performed.

In this document, various terms are used to denote a low-power state ina wireless device, where this state is designed to preserve energy inthe wireless device, while still enabling reasonably fast networkaccess, when this is needed. These terms include “idle”, “dormant”,“inactive”, where “idle” may correspond to the RRC_IDLE state in thecellular communication system referred to as Long Term Evolution (LTE)and/or the 5^(th) generation system currently being standardized by thestandardization organization 3^(rd) Generation Partnership Project(3GPP), denoted “New Radio” (NR), while “dormant” and “inactive” maycorrespond to the RRC_INACTIVE state in NR. Correspondingly, the terms“connected” and “active” are used to denote a state of a wirelessdevice, which is designed for active data communication and fast networkaccess. The terms “connected” and “active” may correspond to the RRCCONNECTED state in LTE and/or NR.

SUMMARY

According to one or more embodiments herein, a user equipment determinesthe set of beams on which to perform a beam sweep or scan, based on theuser equipment's orientation (relative to Earth). The user equipmentbases the beam set determination on its orientation so that the beam setdoes not include any beam pointing in certain predefined direction(s),such as vertically down towards the ground and/or up towards the sky.Beams in the predefined direction(s) may be excluded for instance on thebasis that transmit or receive performance is not likely to meetperformance criteria in the predefined direction(s), e.g., because it isnot likely that any access node or other wireless communicationequipment exists in the predefined direction(s).

In some embodiments, the predefined nature of the excluded direction(s)means that the user equipment does not dynamically determine thedirection(s), e.g., based on measuring the geographical position atwhich an access node or other wireless communication equipment existsrelative to the user equipment. The predefined direction(s) may even bestatically configured at the user equipment. In these and otherembodiments, therefore, the predefined direction(s) may be excluded froma beam sweep or scan even upon user equipment startup, during initialaccess, while in an inactive state, or at any other time which precludesor limits the ability of the user equipment to measure or receiveinformation indicating the direction in which other wirelesscommunication equipment actually exists. In any event, excluding beamsfrom the beam set in this way advantageously reduces the size of thebeam set to be scanned and correspondingly decreases thetransmit/receive delay, radio resource consumption, energy consumption,and/or interference attributable to the beam sweep or scan.

More particularly, embodiments herein include a method performed by auser equipment configured for use in a wireless communication system.The method comprises detecting an orientation of an equipment coordinateframe defined for the user equipment relative to an earth coordinateframe defined for Earth. The orientation may be detected for instancebased on one or more measurements performed by one or more sensors ofthe user equipment (e.g., a tilt sensor, a compass, a gravity sensor,etc.), and/or based on detecting which type of application the userequipment executes. In any event, the method also comprises determining,based on the detected orientation, a set of beams defined in theequipment coordinate frame which does not include any beam pointing inone or more predefined directions in the earth coordinate frame. Themethod further comprises performing a beam sweep or scan on thedetermined set of beams.

In some embodiments, for example, the one or more predefined directionsinclude a vertically down direction and/or a vertically upwarddirection. In fact, in some embodiments, the one or more predefineddirections include directions within a predefined downward cone that iscentered around a vertically down direction in the earth coordinateframe and that extends in the vertically down direction from a vertex atthe user equipment. The one or more predefined directions mayalternatively or additionally include directions include directionswithin a predefined upward cone that is centered around a verticallyupward direction in the earth coordinate frame and that extends in thevertically upward direction from a vertex at the user equipment.

In some embodiments, determining the set of beams comprises selectingthe set of beams from multiple sets of beams predefined for differentdetectable orientations of the equipment coordinate frame relative tothe earth coordinate frame. In this case, each of the multiple sets ofbeams does not include any beam pointing in the one or more predefineddirections in the earth coordinate frame. Alternatively, determining theset of beams may comprise identifying that one or more candidate beamspoint in the one or more predefined directions and forming the set ofbeams on which to perform the beam sweep or scan by either subtractingthe one or more identified candidate beams from the set or adding beamsto the set other than the one or more identified candidate beams.

In some embodiments, the method further comprises deciding whether theset of beams is to not include any beam pointing in at least one of theone or more predefined directions, based on evaluating one or morepredefined criteria. In one embodiment, for example, at least onecriterion of the one or more predefined criteria comprises types ofaccess nodes between which the user equipment is or will hand off.Alternatively or additionally, at least one criterion of the one or morepredefined criteria comprises an altitude at which the user equipment isdetected, estimated, or assumed to be located. In still otherembodiments, at least one criterion of the one or more predefinedcriteria comprises whether the user equipment is located indoors oroutdoors.

In any of the above embodiments, performing the beam sweep or scan maycomprise performing the beam sweep or scan during or before a procedurefor initial access to the wireless communication system, while the userequipment is in an idle or inactive state or is performing a procedurefor transitioning from an idle or inactive state to a connected state,or during or in preparation of a handover procedure.

Note that the method in some embodiments further comprises receivingsignaling from a network node indicating a number of beams that are orthat are to be included in the determined set of beams.

Embodiments herein further include corresponding apparatus, computerprograms, and carriers (e.g., computer-readable medium).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram of a wireless communication system thatincludes a user equipment according to some embodiments herein.

FIG. 1B is a block diagram of an equipment coordinate frame defined fora user equipment according to some embodiments.

FIG. 2A is a block diagram of a beam set determined according to one ormore embodiments herein for performing a beam sweep or scan.

FIG. 2B is a block diagram of a beam set determined according to one ormore other embodiments herein for performing a beam sweep or scan.

FIGS. 3A-3D are block diagrams of different candidate beam setsdetermined according to one or more embodiments herein for performing abeam sweep or scan.

FIG. 4 is a logic flow diagram of a method performed by a user equipmentaccording to some embodiments herein.

FIG. 5A is a block diagram of a user equipment according to someembodiments herein.

FIG. 5B is a block diagram of a user equipment according to otherembodiments herein.

DETAILED DESCRIPTION

FIG. 1A shows a user equipment 10 (UE) in a wireless communicationsystem 12 (e.g., a 5G system, such as the 5G system currently beingstandardized by the standardization organization 3^(rd) GenerationPartnership Project (3GPP), denoted New Radio (NR)) according to someembodiments. The user equipment 10 is configured to perform a beam sweepor scan. The user equipment 10 in this regard determines a set 14 ofbeams 14-1, 14-2, . . . , 14-N on which to perform the beam sweep orscan, and then performs the beam sweep or scan on that set 14 of beams.This may involve for instance transmitting or receiving referencesignals on each of the beams in the set 14, and comparing the resultingperformance (e.g., signal quality) on the beams. As a result of the beamsweep or scan, the user equipment 10 may select one or more of the beamsin the set 14 as being the beam(s) on which to transmit or receive othersignals, e.g., over a user data channel or a control channel.

The user equipment 10 according to some embodiments herein determinesthe set 14 of beams on which to perform the beam sweep or scan, based onthe user equipment's orientation. The user equipment 10 bases the beamset determination on its orientation so that the set 14 does not includeany beam pointing in one or more predefined directions, e.g., avertically down direction towards the ground. In some embodiments,excluding any such beam from the set 14 in this way advantageouslyreduces the size of the set 14 and correspondingly decreases thetransmit/receive delay, radio resource consumption, energy consumption,and/or interference attributable to the beam sweep or scan.

More particularly in this regard, FIG. 1A shows that an equipmentcoordinate frame 10A is defined for the user equipment 10. Thisequipment coordinate frame 10A defines the local frame of reference ofthe user equipment 10 in two dimensional or three dimensional space.FIG. 1B, for example, shows that the equipment coordinate frame 10A maybe described in three dimensions by coordinate axes x, y, and z, withthe origin aligned to the center of the user equipment 10. As shown inthis example, the x-axis is defined in the plane of the equipment'sscreen 10B with positive towards the right of the screen, the y-axis isdefined in the plane of the screen 10B with positive towards the top ofthe screen, and the z-axis is defined perpendicular to the plane of thescreen 10B with positive extending away from the screen. In otherembodiments, of course, the coordinate axes may be defined with respectto something other than a screen (e.g., a keyboard, an antenna, a centerof the user equipment, etc.), especially where the user equipment 10lacks any such screen.

FIG. 1A also shows that an earth coordinate frame 16A is defined forEarth 16. The earth coordinate frame 16A may be aligned based on thegravity and standard magnetic orientation of the Earth. For example, theearth coordinate frame 16A may be described in three dimensions bycoordinate axes x, y, and z, with the x-axis representing the east-westdirection, the y-axis representing the north-south direction, and thez-axis representing the vertically up-down direction, perpendicular toEarth's ground.

The user equipment 10 is configured to detect the orientation of itsequipment coordinate frame 10A relative to the earth coordinate frame16A (in one or more dimensions or coordinate axes of the frames 10A,16A), so as to detect the user equipment's orientation relative to Earth16. The user equipment 10 may for instance detect such orientation basedon one or more measurements performed by one or more sensors of the userequipment 10 (e.g., a tilt sensor, a compass, a gravity sensor, i.e.,accelerometer, and/or another type of sensor internal to the userequipment 10). The measurement(s) in some embodiments indicate therotation (e.g., in degrees) between the equipment and earth coordinateframes 10A, 16A as roll, pitch, and/or yaw values, whereas in otherembodiments the measurement(s) additionally or alternatively indicatethe proper acceleration of the user equipment 10, with or without theeffects of gravity excluded, in one or more dimensions of the equipmentcoordinate frame 10A.

Alternatively or additionally, the user equipment 10 may detect itsorientation based on which type of application the user equipment 10(currently) executes. For example, the user equipment 10 may associateexecution of a voice call application (without hands-free) with the userequipment 10 being in a predefined orientation consistent with placementnear a user's head for a call, e.g., in a mostly vertical or “portrait”orientation. In this case, then, the user equipment 10 may detect thepredefined orientation when it detects execution of the voice callapplication, even without explicit sensor measurements. The userequipment 10 may of course associate execution of other types ofapplications (e.g., photo/video applications, text or emailapplications, video applications, games) with other predefinedorientations (e.g., landscape). Moreover, the user equipment 10 in someembodiments may dynamically adjust the orientations associated withapplications, using sensor measurements taken during applicationexecution, so as to effectively learn or predict the actual orientationsthat exist when those applications execute. As these embodimentsdemonstrate, therefore, the user equipment 10 may generally detect itsorientation relative to Earth as being a certain measured, estimated, orpredicted orientation, using one or more types of orientation-detectingapproaches.

No matter the particular way the user equipment 10 detects itsorientation relative to Earth 16, the user equipment 10 leveragesknowledge of its orientation in order to determine the set 14 of beamson which to perform a beam sweep or scan. The user equipment 10 inparticular determines a set 14 of beams defined in the equipmentcoordinate frame 10A which does not include any beam pointing in one ormore predefined directions in the earth coordinate frame 16A. Thepredefined direction(s) may be excluded based on an estimate orassumption that transmit or receive performance is unlikely to meetperformance criteria on beams pointing in the predefined direction(s),e.g., because no access node or other wireless communication equipmentwith which the user equipment 10 desires to communicate is likely toexist in the predefined direction(s). Beams pointing in the predefineddirection(s) may therefore be deemed by the user equipment 10 as sounreasonable or unlikely to be selected that they are proactivelyexcluded from the set 14 of beams on which a sweep or scan will beperformed; that is, they are excluded from the set 14 even withoutevaluating their performance.

FIG. 1A, for example, shows that the set 14 of beams does not includeany beam pointing in a vertically down direction 16B in the earthcoordinate frame 16A. The vertically down direction 16B may be excludedbased on the assumption or estimation that no access node or otherwireless communication equipment is likely to exist in the verticallydown direction 16B (e.g., towards the ground). Because the set 14 isdetermined based on the equipment's orientation relative to Earth 16,the set 14 of beams in this regard may exclude any beam in thevertically down direction 16B even if the equipment's coordinate frame10A is disoriented with respect to the earth coordinate frame 16A (e.g.,such that the vertically down direction as defined in the equipmentcoordinate frame 10A is not aligned with the vertically down direction16B as defined in the earth coordinate frame 16B). Of course, althoughFIG. 1A just shows excluding any beam pointing in the vertically downdirection 16B, the set 14 of beams may alternatively or additionally notinclude any beam pointing in one or more other directions. For example,in some embodiments, the set 14 does not include any beam pointing indirections within a predefined downward cone that is centered around thevertically down direction 16B and that extends in the vertically downdirection 16B from a vertex at the user equipment 10.

Alternatively or additionally, the set 14 of beams may not include anybeam pointing in a vertically upward direction 16C in the earthcoordinate frame 16A. The vertically upward direction 16C may similarlybe excluded based the assumption or estimation that no access node orother wireless communication equipment is likely to exist in thevertically upward direction 16C (e.g., straight up towards the sky). Ofcourse, in some embodiments, the set 14 also or alternatively does notinclude any beam pointing in directions within a predefined upward conethat is centered around the vertically upward direction 16C and thatextends in the vertically upward direction 16C from a vertex at the userequipment 10. In any event, note that exclusion of the vertically upwarddirection 16C and/or the vertically downward direction 16B may justinvolve the user equipment 10 detecting its orientation in twodimensions (relative to the earth's horizontal plane), as opposed tothree dimensions.

No matter the particular predefined direction(s), beams pointing in thedirection(s) may be excluded from the set 14 in any number of ways. Insome embodiments, for example, the user equipment 10 adapts or activelyforms the set 14 of beams on which to perform the beam sweep or scan.The user equipment 10 may for instance add to the set 14 beams otherthan those pointing in the predefined direction(s), or subtract from theset 14 any beam pointing in the predefined direction(s). FIG. 2Aillustrates one example in this regard.

As shown in FIG. 2A, the user equipment 10 is configured with acomprehensive set 18 of candidate beams. The set 18 of candidate beamsis comprehensive in the sense that it nominally includes beams pointingin multiple possible directions in the equipment coordinate frame 10A,irrespective of whether those beams (depending on the user equipment'sorientation) may point in the predefined direction(s) in the earthcoordinate frame 16A to be excluded from a beam sweep or scan. FIG. 2 inthis regard shows twenty-four beams 18-1, 18-2, . . . , 18-24 thatrespectively point in twenty-four directions in the equipment coordinateframe 10A.

The user equipment 10 is configured to form the set 14 of beams on whichto perform a beam sweep or scan from this comprehensive set 18 ofcandidate beams. In particular, the user equipment 10 identifies, basedon the orientation of its equipment coordinate frame 10A relative to theearth coordinate frame 16A, which candidate beams in the comprehensiveset 18, if any, point in the one or more predefined directions in theearth coordinate frame 16A (e.g., by translating between the coordinateframes 10A, 16A). In FIG. 2A's example, the user equipment 10 identifiesthat candidate beams 18-23, 18-24, and 18-1 point in directions within apredefined downward cone 16D centered around the vertically downwarddirection 16B, and that candidate beams 18-11, 18-12, and 18-13 point indirections within a predefined upward cone 16E centered around thevertically upward direction 16C. The user equipment 10 accordingly formsthe set 14 of beams on which to perform a beam sweep or scan such thatthe set 14 does not include the identified candidate beam(s). In theexample, this means the user equipment 10 forms the set 14 of beams sothat the set 14 does not include any of beams 18-1, 18-11, 18-12, 18-13,18-23, or 18-24. All other candidate beams may be included, absentadditional information justifying their exclusion. The user equipment 10may form the set 14 by for instance adding to the set 14 candidate beamsother than those beams to be excluded, or by subtracting from the set 14those beams to be excluded.

The user equipment 10 may adjust the set 14 or otherwise form the set 14to include/exclude other beams to account for any change in the detectedorientation of the equipment coordinate frame 10A relative to the earthcoordinate frame 16A. FIG. 2B shows for example that the user equipment10 is rotated in orientation as compared to FIG. 2A. Based on thisdetected orientation, the user equipment 10 may adjust or otherwise formthe set 14 so that it instead excludes candidate beams 18-1, 18-2, 18-3,18-13, 18-14, and 18-15, since with this orientation those are thecandidate beams pointing in directions within the predefined upward anddownward cones 16D, 16E.

In other embodiments, the user equipment 10 selects the set 14 of beamson which to perform the beam sweep or scan from multiple candidate setsof beams predefined for different detectable orientations of theequipment coordinate frame 10A relative to the earth coordinate frame16A. In this case, each of the multiple candidate sets of beams does notinclude any beam pointing in the one or more predefined directions inthe earth coordinate frame 16A. In this case, therefore, rather thanselecting the beams to include in or exclude from the set 14, the userequipment 10 instead may select the set 14 from multiple sets that arealready preconfigured to exclude the beam(s) pointing in the predefineddirection(s) in the earth coordinate frame 16A.

FIGS. 3A-3D illustrate as an example multiple candidate sets 18A-18D ofbeams predefined for different detectable orientations. Each candidateset 18A-18D does not include any beam pointing in predefineddirection(s) in the earth coordinate frame 16A (e.g., vertically downand up directions 16B, 16C), e.g., since each candidate set ispreconfigured for a certain user equipment orientation. When the userequipment 10 detects its orientation as being that shown in FIG. 3A, theuser equipment 10 selects candidate set 18A as the set 14 on which toperform a beam sweep or scan. Conversely, when the user equipment 10detects its orientation as being that shown in FIG. 3B, the userequipment 10 selects candidate set 18B as the set 14 on which to performa beam sweep or scan. The same can be said for sets 18C and 18D. Inthese and other embodiments, therefore, the user equipment 10 may simplyselect the set 14 on which to perform a beam sweep or scan as a functionof its detected orientation, e.g., according to a mapping that mapsdifferent orientations to respective sets of beams.

As a further example, some attractive directions to have preconfiguredcandidate sets of beams for is a full circle (360 degrees) of suitablyspaced beam directions (i.e. a suitable granularity) with a certainangle, e.g. 30 degrees upwards, in relation to the horizontal plane(e.g. in terms of a polar angle in a spherical coordinate system fixedto the horizontal plane). As the user equipment 10 may be tilted in anyway in relation to the horizontal plane, the user equipment 10 should beprepared for having the horizontal plane in an arbitrary angle inrelation to the user equipment 10 (in practice, a set of horizontalplane angles/inclinations would have to be chosen with a suitablegranularity) and preconfigure candidate beam sets for beam directionswith the desired angle in relation to any of these possible horizontalplane angles in relation to the user equipment 10. That is, for eachchosen relative horizontal plane angle the user equipment 10 should beprepared with a candidate set of beams, together covering the fullcircle (360 degrees) with suitably spaced beam directions with thedesired angle, e.g. 30 degrees upwards, in relation to the horizontalplane.

Note that the above is merely an example and the total number ofpre-configured beam sets/beam directions may not only cover a certainangle in relation to the horizontal plane, but also other directions,e.g. other angles in relation to the horizontal plane. Also note that,although the horizontal may be a suitable reference for beam directions(and corresponding beam sets), other references could also be used, e.g.the vertical direction.

In this regard, if the user equipment 10 has a uniform array, then thevertical dimension (e.g. the polar angle in a spherical coordinatesystem fixed to the horizontal plane) of the estimated direction ofarrival in one azimuth can be used in other azimuths as well (i.e.“extrapolation” of the polar angle). That is, if the user equipment 10has a uniform antenna array, the antenna configuration for just one beammay be preconfigured for each possible user equipment orientation, andthen the antenna configurations for the rest of the beams in the set forthat user equipment orientation may be inferred or extrapolated from thesingle preconfigured antenna configuration. But there is the challengethat the directivity of a non-uniform array at the user equipment 10 isharder to “extrapolate” to directions other than the particular azimuthjust measured. Therefore, each predefined beam set may span the wholeazimuth span (360 degrees). That is, the antenna configurations of allthe beams in the set may have to be preconfigured for such a userequipment.

No matter the particular way that the user equipment 10 excludes beamspointing in predefined direction(s), such exclusion in some embodimentsis unconditional. That is, the set 14 of beams on which the equipment 10performs a beam sweep or scan unconditionally excludes any beam pointingin one or more of the predefined direction(s) (e.g., in the verticallydownward direction 16B). This may be the case for instance if it isalways assumed that no access node or other wireless communicationequipment is likely to exist in a predefined direction.

In other embodiments, exclusion of any beam pointing in one or more ofthe predefined direction(s) is conditional. That is, the set 14 of beamson which the equipment 10 performs a beam sweep or scan conditionallyexcludes any beam pointing in one or more of the predefineddirection(s), depending on whether one or more conditions are met. Inthis case, therefore, the user equipment 10 may be configured to decidewhether the set of beams is to not include any beam pointing in one ormore of the predefined directions, based on evaluating one or morepredefined criteria. The criteria may concern for instance the types ofaccess nodes between which the user equipment is handing off or willhand off, an altitude at which the user equipment is detected,estimated, or assumed to be located, and/or characterization of theenvironment in which the user equipment is located (e.g., indoors vs.outdoors).

For instance, the set 14 of beams may conditionally exclude any beampointing in the vertically upward direction 16C, if one or moreconditions are met. For instance, the vertically upward direction 16Bmay be excluded if the user equipment 10 is handing off or will hand offbetween macro (i.e., high-power) access nodes or cells (i.e., cells withthe widest coverage area, as opposed to micro or pico cells). Indeed, insuch a handover scenario, the user equipment 10 is unlikely to belocated straight below the macro access nodes' antennas, meaning that abeam pointing in the vertically upward direction 16C is unlikely to haveperformance sufficient for selection. On the other hand, the verticallyupward direction 16B may not be excluded if the user equipment 10 ishanding off or will hand off from a macro cell to a pico cell, or from apico cell to another pico cell (e.g., in an indoor scenario), since itis possible in these cases that the user equipment 10 is locatedstraight below the pico access node's antenna(s).

Similarly, the set 14 of beams may conditionally exclude any beampointing in the vertically downward direction 16B, if one or moreconditions are met. For instance, the vertically downward direction 16Bmay be excluded unless the user equipment 10 is measured, estimated, orassumed to be located at a relatively high altitude or in a certainenvironment (e.g., indoors) such that an access node may be locatedbelow the user equipment 10.

As these examples demonstrate, the excluded direction(s) may bepredefined even in embodiments described above where the user equipment10 conditions exclusion of any beam pointing in a direction on one ormore conditions being met. The user equipment 10 in a broad sensetherefore may be configured to determine a set 14 of beams on which toperform a beam sweep or scan that unconditionally or conditionally doesnot include any beam pointing in one or more predefined directions. Inthe conditional case, an excluded direction is predefined (e.g., asvertically upward or downward), whereas the decision as to whether anybeam pointing in that predefined direction is to be excluded may bedynamically determined based on whether condition(s) are met. That is,it is not the direction that the user equipment 10 dynamicallydetermines, but rather whether to exclude any beam pointing in thatdirection.

Accordingly, in one or more embodiments, the predefined nature of theexcluded direction(s) means that the user equipment 10 does notdynamically determine the direction(s). The user equipment 10 forinstance does not dynamically determine the predefined direction(s) toconditionally or unconditionally exclude based on measuring thegeographical position or angle at which an access node or other wirelesscommunication equipment does or does not exist relative to the userequipment 10, based on receiving signaling indicating such geographicalposition or angle, and/or based on any other information that indicatesthe presence or absence of an access node or other wirelesscommunication equipment in a certain direction. Without the userequipment 10 dynamically determining the predefined direction(s), thepredefined direction(s) may even be statically configured at the userequipment 10. The predefined nature of the excluded direction(s) in thissense contributes to processing simplicity and power efficiency at theuser equipment 10.

In these and other embodiments, therefore, the predefined direction(s)may be excluded from a beam sweep or scan even upon user equipment(cold) startup, during or before initial network access, while in aninactive state, or at any other time which precludes or limits theability of the user equipment 10 to perform positioning measurements orreceive information indicating the direction in which other wirelesscommunication equipment (e.g., an access node) actually exists.

More particularly, the user equipment 10 in some embodiments performsthe beam sweep or scan on the determined set 14 of beams during orbefore a procedure for initial access to the system 12, during aprocedure for state transition (e.g., idle/dormant to connected/activestate), and/or while the user equipment is in an idle or inactive state.The user equipment 10 may for instance perform a beam sweep bytransmitting uplink signals (e.g., random access preamble signals) onthe determined set 14 of beams, and/or perform a beam scan by receivingdownlink signals (e.g., pilot signals and/or system information) on thedetermined set 14 of beams. The user equipment 10 may transmit and/orreceive these signals one signal at a time in case of analog beamformingor may transmit and/or receive at least some of the signalssimultaneously in parallel in case of digital beamforming.

Note that some access nodes may be deployed in the system 12 as boosternodes for high data rates. Such access nodes may not transmit any pilotsignals, unless requested, e.g., when requested by another access nodein conjunction with handover. Hence, these access nodes may not beavailable for initial access or state transition, but instead onlyavailable via handover from another access node. But even though nottransmitting any pilot signals, the access nodes may still listen forrandom access transmissions (e.g., random access preamble signals) andmay respond to them for access.

Alternatively or additionally, the user equipment 10 in some embodimentsperforms the beam sweep or scan on the determined set 14 of beams duringor in preparation of a handover procedure. Consider for instance adownlink measurement based handover that uses beamforming. In this case,whenever handover is performed (e.g., from one access node or frequencyto another), the user equipment 10 may perform a beam scan on thedetermined set 14 of beams (which are receive beams in this case), in anattempt to detect a synchronization and/or beam identification signal(e.g., a synchronization signal, a synchronization and reference signal,a pilot signal, a Mobility and access Reference Signal, MRS, or aChannel State Information Reference Signal, CSI-RS, or any other type ofreference signal), where the beam identification signal identifies thetransmit beam over which that signal is transmitted. The user equipment10 may then report back information indicating which transmit beam(s)the user equipment 10 detected with at least a certain performance, tosupport selection of the target access node (and transmit beam) for thehandover. The user equipment 10 may for instance report the result ofits measurements to the source access node, e.g., using a radio resourcecontrol (RRC) message. Or, the user equipment 10 may send an uplinksignal directly to the candidate access node that transmitted thedownlink beam signal that the user equipment 10 perceived as the best(e.g., best signal quality). The uplink signal may be for instance anUplink Synchronization Signal (USS) or a random access preamble.Reporting directly to the best candidate access node is a fast andresource efficient way of reporting, and is more robust in the case offast deterioration of the serving link to the source access node.

Alternatively or additionally, the user equipment 10 may perform a beamsweep on the determined set 14 of beams (which are transmit beams inthis case), in order to transmit an uplink signal that explicitly orimplicitly reports the result of its measurements. The user equipment 10may for instance repeat the uplink signal on each beam in the set 14,one at a time.

Consider also an uplink measurement based handover that usesbeamforming. In this case, the user equipment 10 performs a beam sweepon the determined set 14 of beams (which are transmit beams in thiscase). The user equipment 10 in this regard transmits uplink signals(e.g., sounding signals, reference signals, or a combination thereof) onthe beams in the set 14. Candidate cells or access nodes measure theseuplink signals in terms of quality. One of those candidate cells oraccess nodes is then selected as a target for handover, e.g., as afunction of measured uplink quality and/or an estimate of downlinkquality based on uplink/downlink reciprocity. The user equipment 10 mayreceive information indicating the handover target selected by thenetwork and then perform handover to the indicated target.

The above examples generally illustrate therefore that there are variouscases where the user equipment 10 may need to perform a beam sweep orscan. Such a beam sweep or scan has heretofore significantly increasedboth delay and resource consumption as well as increased theinterference in the system. The increased delay is not only aperformance issue in itself, but in handover cases the increased delayalso increases the risk of handover failure and loss of the radio link(radio link failure). The consumed resources are both radio resourcesand energy (reducing the battery lifetime in the user equipment). Thiscan affect uplink transmit resources, downlink transmit resources (forrepetition of downlink beams to support user equipment beam scanning)and uplink receive resources in access nodes.

One or more embodiments herein generally leverage spatial information(e.g., rotation or orientation) from the user equipment's internalsensors to eliminate unreasonable or unlikely beam directions which areirrelevant (or the most likely to be irrelevant) for a user equipment'sbeam sweep or scan. The reference case or default solution without suchelimination would be a full beam sweep or scan at the user equipment inall possible directions. One or more embodiments herein thereby reducethe number of beam directions a user equipment includes in a beam sweepor scan procedure, e.g., in conjunction with handover or initial accessor state transition. This serves to reduce the delay of the concernedprocedure, which is good for the performance of the service delivered bythe network. In the handover case, the reduced delay also reduces therisk for handover failure and loss of the radio link (radio linkfailure). In addition, the downsizing of the beam sweep or scan alsoreduces the interference in the system as well as the resourceconsumption, including transmit/receive radio resources and energy(thereby extending the battery lifetime in the user equipment).According to some embodiments, the user equipment may also provide radioresource measurements faster to the network compared to the case where afull beam scan needs to be done e.g. in the case the downlinkmeasurement based handover for measuring downlink MRSs/beams. That mayprevent the user equipment from spending too much time performing radioresource measurements and potentially losing the link before reportingthe MRS/beam quality to the network.

Note that, in some embodiments where the beam sweep or scan is performedduring or in preparation for handover, the source access node instructsthe user equipment 10 (when configuring the user equipment for thedownlink beam sweep measurement procedure) of how many receive beams totry for each candidate downlink beam and/or the number of transmit beamsto use for the uplink signal transmission. The source access node insome embodiments bases the number of receive/transmit beams oninformation such as the urgency of the handover procedure (e.g. how fastthe serving link can be assumed to deteriorate and consequently how longdelay is acceptable for the handover), etc. Yet another alternative isthat the network instructs the user equipment 10 of how many receiveand/or transmit beams to use in the system information. This isespecially beneficial in the case where multiple user equipments wouldbenefit from the same downlink signal (e.g. MRS) beam sweep, e.g. in thecase of common periodic MRSs. In that case, the network may decide toconfigure the downlink MRS beam sweep, e.g. for the user equipmentsrequiring the greatest number of DL beam repetitions (for receive beamtrials).

Also note that, in some embodiments, the user equipment 10 is configuredto perform a beam sweep or scan on the determined (reduced) set 14 ofbeams as a first stage or pass, with predefined direction(s) excluded.If the beam sweep or scan proves insufficient with use of the reducedset 14 of beams, e.g., the user equipment 10 may complement the initialbeam sweep or scan with a second pass sweep or scan on beams pointing inthe predefined direction(s) that were initially excluded in the firstpass.

The system 12 in some embodiments is a 5G system, or any system thatuses very high frequency ranges for communication (e.g., at or above 10GHz) and/or uses very high-gain narrow beamforming. For such highfrequency spectrum, the atmospheric, penetration and diffractionattenuation properties can be much worse than for lower frequencyspectrum. In addition, the receiver antenna aperture, as a metricdescribing the effective receiver antenna area that collects theelectromagnetic energy from an incoming electromagnetic wave, isinversely proportional to the frequency, i.e., the link budget would beworse for the same link distance even in a free space scenario, ifomnidirectional receive and transmit antennas are used. This motivatesthe usage of beamforming to compensate for the loss of link budget inhigh frequency spectrum. Beamforming may be used at the transmitter, atthe receiver, or both. In a large part of the spectrum planned for 5Gdeployments, the preferred configuration is to use a large antenna arrayat the Access Node (AN) and a small number of antennas at the userequipment. The large antenna array at the AN enables high-order transmitbeamforming in the downlink.

For the above reasons, the system 10 may make heavy use of high-gain,narrow beamforming, which will enable high data rate transmissioncoverage also to very distant user equipment which would notrealistically be covered with normal sector-wide beams, which have lowerantenna gain. In these and other cases, even performing synchronizationor exchanging some initial control signaling messages at the handovertarget may require selection of a sufficiently good beam direction inorder for the access node and the user equipment 10 to hear each othersufficiently well. Nonetheless, a beam as used herein may be any sizebeam created through beamforming, i.e., a beam may be a narrow beam asdescribed above or even a sector-wide beam.

Note too that although beams were by necessity illustrated in thefigures in one dimensional space, beams herein may have coverage areasthat are described in one, two, or three dimensional space. Moreover,although a signal has been referred to as being transmitted “on” a beam,a signal may in other senses be said to be transmitted “in” or “over” or“using” a beam. Yet another alternative expression is that the signaltransmission is “beamformed”.

Embodiments herein are generally applicable however to any type ofwireless communication system 12 which employs beamforming. Indeed,embodiments may use any of one or more communication protocols known inthe art or that may be developed, such as IEEE 802.xx, CDMA, WCDMA, GSM,LTE, UTRAN, WiMax, or the like, also including 5^(th) generation (5G)systems, such as the 5G system currently being standardized by 3GPP,denoted New Radio (NR). Accordingly, although sometimes described hereinin the context of 5G, the principles and concepts discussed herein areapplicable to 4G systems and others.

A user equipment is any type of device capable of communicating with aradio network node or another user equipment wirelessly over radiosignals. A user equipment may therefore refer to a mobile station, alaptop, a smartphone, a machine-to-machine (M2M) device, a machine-typecommunications (MTC) device, a narrowband Internet of Things (loT)device, etc. That said, it should be noted that a user equipment doesnot necessarily have a “user” in the sense of an individual personowning and/or operating the device. A user equipment may also bereferred to as a wireless communication device, a radio device, a radiocommunication device, a wireless terminal, or simply a terminal—unlessthe context indicates otherwise, the use of any of these terms isintended to include device-to-device UEs or devices, machine-typedevices or devices capable of machine-to-machine ormachine-to-human/human-to-machine communication, sensors equipped with awireless device, wireless-enabled table computers, mobile terminals,smart phones, laptop-embedded equipped (LEE), laptop-mounted equipment(LME), USB dongles, wireless customer-premises equipment (CPE), etc. Inthe discussion herein, the terms machine-to-machine (M2M) device,machine-type communication (MTC) device, wireless sensor, and sensor mayalso be used. It should be understood that these devices may be UEs, butmay be generally configured to transmit and/or receive data withoutdirect human interaction.

In an IoT scenario, a user equipment as described herein may be, or maybe comprised in, a machine or device that performs monitoring ormeasurements, and transmits the results of such monitoring measurementsto another device or a network. Particular examples of such machines arepower meters, industrial machinery, or home or personal appliances, e.g.refrigerators, televisions, personal wearables such as watches etc. Inother scenarios, a user equipment as described herein may be comprisedin a vehicle and may perform monitoring and/or reporting of thevehicle's operational status or other functions associated with thevehicle.

As used herein, a “radio network node” or access node refers to networkequipment capable, configured, arranged and/or operable to communicatedirectly or indirectly with a user equipment and/or with other equipmentin the wireless communication system that enable and/or provide wirelessaccess to the user equipment. Examples of network equipment include, butare not limited to, base stations (BSs), radio base stations, Node Bs,multi-standard radio (MSR) radio nodes such as MSR BSs, evolved Node Bs(eNBs), gNodeBs (gNBs), femto base stations, pico base stations, microbase stations, macro base stations, one or more (or all) parts of adistributed radio base station such as centralized digital units and/orremote radio units (which may or may not be integrated with an antennaas an antenna integrated radio), network controllers, radio networkcontrollers (RNCs), base station controllers (BSCs), relay nodes, relaydonor node controlling relays, base transceiver stations (BTSs), accesspoints (APs), radio access points, transmission points, transmissionnodes, Remote Radio Units (RRUs), Remote Radio Heads (RRHs), nodes in adistributed antenna system (DAS), Multi-cell/multicast CoordinationEntities (MCEs), core network nodes (e.g., MSCs, MMEs), O&M nodes, OSSnodes, SON nodes, positioning nodes (e.g., E-SMLCs), and/or MDTs. Moregenerally, however, a radio network node may represent any suitabledevice (or group of devices) capable, configured, arranged, and/oroperable to enable and/or provide a user equipment access to thewireless communication network or to provide some service to a userequipment that has accessed the wireless communication network. The listabove is not intended to express just alternative radio network nodes,but to express various examples of classes of network equipment as wellas examples of specific network equipment.

Some embodiments herein are described with reference to a wireless link.A wireless link may take the form of a cell, a sector, a beam, an accessnode, or the like.

In view of the above variations and modifications, FIG. 4 generallyillustrates a method 100 performed by a user equipment 10 configured foruse in a wireless communication system 12 according to some embodiments.As shown, the method 100 includes detecting an orientation of anequipment coordinate frame 10A defined for the user equipment 10relative to an earth coordinate frame 16A defined for Earth 16 (Block110). The method 100 also includes determining, based on the detectedorientation, a set 14 of beams defined in the equipment coordinate frame10A which does not include any beam pointing in one or more predefineddirections in the earth coordinate frame 16A (e.g., vertically downand/or up) (Block 120). The method 100 further includes performing abeam sweep or scan on the determined set 14 of beams (Block 130).

The user equipment 10 as described above may perform any of theprocessing herein by implementing any functional means or units. In oneembodiment, for example, the user equipment 10 comprises respectivecircuits or circuitry configured to perform the steps shown in FIG. 4.The circuits or circuitry in this regard may comprise circuits dedicatedto performing certain functional processing and/or one or moremicroprocessors in conjunction with memory. In embodiments that employmemory, which may comprise one or several types of memory such asread-only memory (ROM), random-access memory, cache memory, flash memorydevices, optical storage devices, etc., the memory stores program codethat, when executed by the one or more processors, carries out thetechniques described herein.

FIG. 5A illustrates a user equipment 10 in accordance with one or moreembodiments. As shown, the user equipment 10 includes communicationcircuitry 210 and processing circuitry 220. The communication circuitry210 is configured to transmit and/or receive information to and/or fromone or more other nodes, e.g., via any communication technology. Thecommunication circuitry 210 may do so for instance via one or moreantennas, which may be internal or external to the user equipment 10. Insome embodiments, the communication circuitry 210 comprises radiocircuitry. The processing circuitry 220 is configured to performprocessing described above, e.g., in FIG. 4, such as by executinginstructions stored in memory 220. The processing circuitry 220 in thisregard may implement certain functional means, units, or modules.

FIG. 5B illustrates a user equipment 10 in accordance with one or moreother embodiments. As shown, the user equipment 10 implements variousfunctional means, units, or modules, e.g., via the processing circuitry220 in FIG. 5A and/or via software code. These functional means, units,or modules, e.g., for implementing the method in FIG. 4, include forinstance an orientation detecting module or unit 310 for detecting anorientation of an equipment coordinate frame defined for the userequipment relative to an earth coordinate frame defined for Earth. Alsoincluded is a beam set determination module or unit 320 for determining,based on the detected orientation, a set of beams defined in theequipment coordinate frame which does not include any beam pointing inone or more predefined directions in the earth coordinate frame. Furtherincluded is a beam sweep or scan module or unit 330 for performing abeam sweep or scan on the determined set of beams.

Those skilled in the art will also appreciate that embodiments hereinfurther include corresponding computer programs.

A computer program comprises instructions which, when executed on atleast one processor of a user equipment 10, cause the user equipment 10to carry out any of the respective processing described above. Acomputer program in this regard may comprise one or more code modulescorresponding to the means or units described above.

Embodiments further include a carrier containing such a computerprogram. This carrier may comprise one of an electronic signal, opticalsignal, radio signal, or computer readable storage medium.

In this regard, embodiments herein also include a computer programproduct stored on a non-transitory computer readable (storage orrecording) medium and comprising instructions that, when executed by aprocessor of a user equipment 10, cause the user equipment 10 to performas described above.

Embodiments further include a computer program product comprisingprogram code portions for performing the steps of any of the embodimentsherein when the computer program product is executed by a user equipment10. This computer program product may be stored on a computer readablerecording medium.

The present invention may, of course, be carried out in other ways thanthose specifically set forth herein without departing from essentialcharacteristics of the invention. The present embodiments are to beconsidered in all respects as illustrative and not restrictive, and allchanges coming within the meaning and equivalency range of the appendedclaims are intended to be embraced therein.

What is claimed is:
 1. A method performed by a user equipment configuredfor use in a wireless communication system, the method comprising:detecting an orientation of an equipment coordinate frame defined forthe user equipment relative to an earth coordinate frame defined forEarth; determining, based on the detected orientation, a set of beamsdefined in the equipment coordinate frame which does not include anybeam pointing in one or more predefined directions in the earthcoordinate frame, wherein determining the set of beams comprisesselecting the set of beams from multiple sets of beams predefined fordifferent detectable orientations of the equipment coordinate framerelative to the earth coordinate frame, and wherein each of the multiplesets of beams does not include any beam pointing in the one or morepredefined directions in the earth coordinate frame; and performing abeam sweep or scan on the determined set of beams.
 2. The method ofclaim 1, wherein the one or more predefined directions include avertically down direction.
 3. The method of claim 1, wherein the one ormore predefined directions include a vertically upward direction.
 4. Themethod claim 1, further comprising deciding whether the set of beams isto not include any beam pointing in at least one of the one or morepredefined directions, based on evaluating one or more predefinedcriteria.
 5. The method of claim 4, wherein at least one criterion ofthe one or more predefined criteria comprises types of access nodesbetween which the user equipment is or will hand off.
 6. The method ofclaim 4, wherein at least one criterion of the one or more predefinedcriteria comprises an altitude at which the user equipment is detected,estimated, or assumed to be located.
 7. The method of claim 4, whereinat least one criterion of the one or more predefined criteria compriseswhether the user equipment is located indoors or outdoors.
 8. The methodof claim 1, wherein determining the set of beams comprises identifyingthat one or more candidate beams point in the one or more predefineddirections and forming the set of beams on which to perform the beamsweep or scan by either subtracting the one or more identified candidatebeams from the set or adding beams to the set other than the one or moreidentified candidate beams.
 9. The method of claim 1, wherein performingthe beam sweep or scan comprises performing the beam sweep or scanduring or before a procedure for initial access to the wirelesscommunication system.
 10. The method of claim 1, wherein performing thebeam sweep or scan comprises performing the beam sweep or scan during orin preparation of a handover procedure.
 11. The method of claim 1,wherein performing the beam sweep or scan comprises performing the beamsweep or scan while the user equipment is in an idle or inactive stateor is performing a procedure for transitioning from an idle or inactivestate to a connected state.
 12. The method of claim 1, furthercomprising receiving signaling from a network node indicating a numberof beams that are or that are to be included in the determined set ofbeams.
 13. The method of claim 1, comprising detecting said orientationbased on one or more measurements performed by one or more sensors ofthe user equipment.
 14. The method of claim 13, wherein the one or moresensors of the user equipment comprise one or more of a tilt sensor, acompass, and a gravity sensor.
 15. The method of claim 1, comprisingdetecting said orientation based on detecting which type of applicationthe user equipment executes.
 16. A user equipment configured for use ina wireless communication system, the user equipment comprising:processing circuitry and a memory, the memory-containing instructionsexecutable by the processing circuitry whereby the user equipment isconfigured to: detect an orientation of an equipment coordinate framedefined for the user equipment relative to an earth coordinate framedefined for Earth; determine, based on the detected orientation, a setof beams defined in the equipment coordinate frame which does notinclude any beam pointing in one or more predefined directions in theearth coordinate frame by selecting the set of beams from multiple setsof beams predefined for different detectable orientations of theequipment coordinate frame relative to the earth coordinate frame,wherein each of the multiple sets of beams does not include any beampointing in the one or more predefined directions in the earthcoordinate frame; and perform a beam sweep or scan on the determined setof beams.
 17. The user equipment of claim 16, wherein the one or morepredefined directions include a vertically down direction.
 18. The userequipment of claim 16, wherein the one or more predefined directionsinclude a vertically upward direction.
 19. The user equipment of claim16, the memory containing instructions executable by the processingcircuitry whereby the user equipment is configured to decide whether theset of beams is to not include any beam pointing in at least one of theone or more predefined directions, based on evaluating one or morepredefined criteria.
 20. The user equipment of claim 19, wherein atleast one criterion of the one or more predefined criteria comprisestypes of access nodes between which the user equipment is or will handoff.
 21. The user equipment of claim 19, wherein at least one criterionof the one or more predefined criteria comprises an altitude at whichthe user equipment is detected, estimated, or assumed to be located. 22.The user equipment of claim 19, wherein at least one criterion of theone or more predefined criteria comprises whether the user equipment islocated indoors or outdoors.
 23. The user equipment of claim 16, thememory containing instructions executable by the processing circuitrywhereby the user equipment is configured to determine the set of beamsby identifying that one or more candidate beams point in the one or morepredefined directions and forming the set of beams on which to performthe beam sweep or scan by either subtracting the one or more identifiedcandidate beams from the set or adding beams to the set other than theone or more identified candidate beams.
 24. The user equipment of claim16, the memory containing instructions executable by the processingcircuitry whereby the user equipment is configured to perform the beamsweep or scan during or before a procedure for initial access to thewireless communication system.
 25. The user equipment of claim 16, thememory containing instructions executable by the processing circuitrywhereby the user equipment is configured to perform the beam sweep orscan during or in preparation of a handover procedure.
 26. The userequipment of claim 16, the memory containing instructions executable bythe processing circuitry whereby the user equipment is configured toperform the beam sweep or scan while the user equipment is in an idle orinactive state or is performing a procedure for transitioning from anidle or inactive state to a connected state.
 27. The user equipment ofclaim 16, the memory containing instructions executable by theprocessing circuitry whereby the user equipment is configured to receivesignaling from a network node indicating a number of beams that are orthat are to be included in the determined set of beams.
 28. The userequipment of claim 16, the memory containing instructions executable bythe processing circuitry whereby the user equipment is configured todetect said orientation based on one or more measurements performed byone or more sensors of the user equipment.
 29. The user equipment ofclaim 28, wherein the one or more sensors of the user equipment compriseone or more of a tilt sensor, a compass, and a gravity sensor.
 30. Theuser equipment of claim 16, the memory containing instructionsexecutable by the processing circuitry whereby the user equipment isconfigured to detect said orientation based on detecting which type ofapplication the user equipment executes.
 31. A non-transitory computerreadable medium having stored thereon a computer program that, whenexecuted by processing circuitry of a user equipment configured for usein a wireless communication system, causes the user equipment to: detectan orientation of an equipment coordinate frame defined for the userequipment relative to an earth coordinate frame defined for Earth;determine, based on the detected orientation, a set of beams defined inthe equipment coordinate frame which does not include any beam pointingin one or more predefined directions in the earth coordinate frame byselecting the set of beams from multiple sets of beams predefined fordifferent detectable orientations of the equipment coordinate framerelative to the earth coordinate frame, wherein each of the multiplesets of beams does not include any beam pointing in the one or morepredefined directions in the earth coordinate frame; and perform a beamsweep or scan on the determined set of beams.
 32. The non-transitorycomputer readable medium of claim 31, wherein the computer program, whenexecuted by the processing circuitry of the user equipment, causes theuser equipment to decide whether the set of beams is to not include anybeam pointing in at least one of the one or more predefined directions,based on evaluating one or more predefined criteria, wherein at leastone criterion of the one or more predefined criteria comprises types ofaccess nodes between which the user equipment is or will hand off. 33.The non-transitory computer readable medium of claim 31, wherein thecomputer program, when executed by the processing circuitry of the userequipment, causes the user equipment to decide whether the set of beamsis to not include any beam pointing in at least one of the one or morepredefined directions, based on evaluating one or more predefinedcriteria, wherein at least one criterion of the one or more predefinedcriteria comprises whether the user equipment is located indoors oroutdoors.